By studying key processes in the carbon cycle, such as photosynthesis, composting and anaerobic digestion, students learn how nature and engineers "biorecycle" carbon. Students are exposed to examples of how microbes play many roles in various systems to recycle organic materials and also learn how the carbon cycle can be used to make or release energy.

In a multi-week experiment, students monitor the core temperatures of two compost piles, one control and one tended, to see how air and water affect microbial activity. They daily aerate and wet the "treated" pile and collect 4-6 weeks' worth of daily temperature readings. Once the experiment is concluded, students plot and analyze their data to compare the behavior of the two piles. They find that the treated pile becomes hotter, an indication that more microbes are active and releasing heat. Through this activity, students see that microbes play a role in composting and how composting can be used as a carbon management process.

In a multi-week experiment, student teams gather biogas data from the mini-anaerobic digesters that they build to break down different types of food waste with microbes. Using plastic soda bottles for the mini-anaerobic digesters and gas measurement devices, they compare methane gas production from decomposing hot dogs, diced vs. whole. They monitor and measure the gas production, then graph and analyze the collected data. Students learn how anaerobic digestion can be used to biorecycle waste (food, poop or yard waste) into valuable resources (nutrients, biogas, energy).

How does infrastructure meet our needs? What happens when we are cut off from that supporting infrastructure? As a class, students brainstorm, identify and explore the pathways where their food, water and energy originate, and where wastewater and solid waste go. After creating a diagram that maps a neighborhood's inputs and waste outputs, closed and open system concepts are introduced by imagining the neighborhood enclosed in a giant dome, cut off from its infrastructure systems. Students consider the implications and the importance of sustainable resource and waste management. They learn that resources are interdependent and that recycling wastes into resources is key to sustain a closed system.

Student teams find solutions to hypothetical challenge scenarios that require them to sustainably manage both resources and wastes. They begin by creating a card representing themselves and the resources (inputs) they need and wastes (outputs) they produce. Then they incorporate additional cards for food and energy components and associated necessary resources and waste products. They draw connections between outputs that provide inputs for other needs, and explore the problem of using linear solutions in resource-limited environments. Then students incorporate cards based on biorecycling technologies, such as algae photobioreactors and anaerobic digesters in order to make circular connections. Finally, the student teams present their complete biorecycling engineering solutions to their scenarios in poster format by connecting outputs to inputs, and showing the cycles of how wastes become resources.

Express yourself through your genes! See if you can generate and collect three types of protein, then move on to explore the factors that affect protein synthesis in a cell.

In a multi-week experiment, student groups gather data from the photobioreactors that they build to investigate growth conditions that make algae thrive best. Using plastic soda bottles, pond water and fish tank aerators, they vary the amount of carbon dioxide (or nutrients or sunlight, as an extension) available to the microalgae. They compare growth in aerated vs. non-aerated conditions. They measure growth by comparing the color of their algae cultures in the bottles to a color indicator scale. Then they graph and analyze the collected data to see which had the fastest growth. Students learn how plants biorecycle carbon dioxide into organic carbon (part of the carbon cycle) and how engineers apply their understanding of this process to maximize biofuel production.